A conventional optical disk includes a plastic base upon which layers of various materials, such as metals, alloys, or dielectrics, are applied. One method of applying the layers of materials is to use a sputter deposition process.
A conventional sputter deposition process is performed using a plasma formed in a sputtering chamber of a sputtering system. The plasma is generated by applying electric power to a low pressure gas in the vacuum chamber. Ions originating within the plasma bombard a target that is formed of a material that is to be deposited on the optical disk. The bombarding ions eject material from the target. The ejected material deposits in a layer on the optical disk.
The present invention includes a sputtering system and methods that may be used to deposit a film on a substrate. The substrate may be an optical disk having a central aperture. The film deposited thereon may include a metal, an alloy, or an insulator, among other possibilities.
In one embodiment, the sputtering system includes a main vacuum chamber. A plurality of sputtering chambers and a load lock are connected to the main vacuum chamber. The sputtering system also includes a plurality of substrate transfer trays, each of which carries an assembly of a substrate, an inner mask, and an outer mask.
A method of using the sputtering system includes loading an unprocessed substrate and its accompanying inner and outer masks onto a transfer tray that is positioned in the load lock. The transfer tray receives, supports, and centers the substrate and masks, while at the same time sealing an access aperture between the load lock and the main vacuum chamber. The transfer tray, substrate and inner and outer masks are subsequently lowered by a lift pedestal onto a carousel in the main vacuum chamber. The carousel indexes the tray (and the substrate and masks supported thereon) through each of the sputtering stations. A lift pedestal beneath the respective sputtering chamber lifts the tray from the carousel and positions the tray so that the substrate thereon can be sputter coated. Meanwhile, the lift pedestal holds the tray over the access opening of the sputtering chamber so as to isolate the sputtering chamber from the main vacuum chamber. Each lift pedestal is supported on a gimbal to correct for any misalignment and lack of parallelism between the tray/pedestal and the surfaces around the access opening. After sputtering, the lift pedestal returns the tray to the carousel. Ultimately, the carousel returns the tray to the load lock so that the processed substrate and its accompanying inner and outer masks may be removed from the sputtering system. Whereupon, the cycle repeats.
The sputtering system of the present invention has numerous useful features. For example, the exemplary substrate transport tray: (1) holds the substrate during processing without touching areas that are sensitive to particles or scratches; (2) supports the substrate on a plurality of projections that are located so that the substrate can be lifted from the tray easily; (3) provides a thermal path for heat generated by the sputtering process to be removed from the substrate and masks; (4) provides centering for the outer mask; (5) provides a means of centering the substrate and inner mask relative to the outer mask; and (6) selectively seals the access opening of each of the sputtering chambers and the load lock chamber without requiring that the carousel itself be lifted. Using the tray to isolate the sputtering chambers and load lock from each other and from the main vacuum chamber allows separate processes to be performed simultaneously under different process conditions (e.g., different pressures), prevents cross-contamination of the processes, and allows the sputtering chambers and load lock to be separately vented to atmosphere.
The exemplary carousel also provides many useful features. For example, the carousel is relatively lightweight for easy rotation, yet holds a plurality of substrate transfer trays. Moreover, the engagement between the trays and the edges of the apertures of the carousel centers the trays relative to the carousel, allows the carousel to rotate at relatively high acceleration and velocity without any slippage of the trays, and allows the trays to be easily placed on or removed from the carousel.
The exemplary lift pedestals center the substrate transfer trays relative to the access aperture of the respective sputtering chamber and the load lock. The metal to metal connections between the lift pedestal and the tray also provides a thermal path for removing heat from the tray.
The exemplary load lock allows the substrate to be horizontally loaded into or unloaded from the sputtering system.